This requires a tight fit inconductive to stock feet though. But, you can use the walls as a Panstand & mount the wooden rails to it, or remove the rails & mount the MG1.5's perforated steel panel directly to the wall.

Essntially, you're making an anechoic TL out of the corner. So, if you want more bass add uphostery stuffing behind it, but beware as the sound will get duller simulatneously. An alternative is to mount thick open cell foam to the wall behind the corner Maggies.

FYI, if you want to minimise the K-horn loading of the tweeter, place the tweeter on the most obtuse side (eg: in the floorplan below the tweeter would be on the inside). So, IMHO, stay away from 45º right triangular prism (wedge) cavities.